1. Field of the Invention
This invention relates to fixation devices used in surgical procedures to the internal fixation of femoral neck fractures. Femoral neck fractures are the most common, and they are especially prevalent in elderly persons suffering from osteoporosis. Many internal fixation devices have been proposed for treating femoral neck fractures, but until now, none of these have included a simple means to make such devices universally applicable to all patients, even though they have a wide variation in their respective femoral neck angles.
2. Description of the Related Art
The following patents are related to fixation devices for the internal fixation of femoral neck fractures:
______________________________________ Patent Number Inventor Date ______________________________________ 2,441,765 Hopkins 1948 2,500.993 Mason 1948 2,801,631 Charnley 1957 3,256,877 Haboush 1966 3,554,193 Konstantinou 1971 5,127,914 Calderale, et al 1992 5,462,547 Weigum 1995. ______________________________________
Hopkins '765 is directed to a surgical device for internal fixation of intertrochanteric fractures of the femur which provides an adjustable angle between the fixation nail and the extension arm to hold the nail in position. The hemispherical end of the fixation nail fits into a socket on the end of the extension arm, the outer surface of which is provided with cooperating serrations or teeth which mesh with matching teeth of a partially spherical washer to secure the nail and the washer at a predetermined angle when a cap screw is tightened into the nail over the washer. Even a small loosening the cap screw which can happen during the fixation period can permit shifting between the nail and the extension arm. Also, the Hopkins device is complex, and relatively expensive to manufacture.
Charnley '631 shows a later device which has a fixed angle between an extension arm and a tubular part which surrounds a fixation screw. A number of fixed angle devices having different angles must be available to the surgeon during the operation so that the optimum angle selection can be made. If the fixation device selected is incorrect, it cannot be adjusted in situ, but must be completely removed, with very serious consequences to the patient.
Haboush '877 is a later development which is somewhat similar to Hopkins in that Haboush also interconnects his fixation nail and plate (extension arm) by means of a ratchet joint (serrations or teeth). Haboush's joint is fastened from the side by screws. Both screws must remained securely fastened during the healing process for this device to work. As with Hopkins, even a slight loosening of either screw could permit a shifting of the angle between the fixation nail and plate. The Haboush device is also complex, and, therefore, expensive to manufacture.
Calderale, et al '914 describe an elongated plate which is secured to the shaft of the femur, and which has a angle joint in its upper end. This plate is disposed at the upper end of the femur just below the greater trochanter, and opposite the femoral head. Adjustable elements 15 receive a pair of screws 8, which extend through the fractured femoral neck and rigidly anchor the shaft of the femur to the femoral head. The elements 15 are spherical, and fit into spherical seats 19. A plate 21 holds the elements in place by tightening connecting member 22. The device is complex, and, therefore, expensive to manufacture. Only slight loosening of member 22 would allow the angle to shift during the healing period.
Weigum '547 is directed to a similar device which comprises a sleeve strap and a trochanter stabilization plate. The sleeve strap includes an integral sleeve which has a fixed angle. The sleeve extends into the trochanter towards the femoral head, and provides a passage for a bone screw. The Weigum apparatus is expensive to use, because a plurality of sleeve straps must be provided with every unit shipped to be sure that one is available having the correct angle for the sleeve. A wide variation between femoral neck angles exists in different patients. As with Charnley, selecting the wrong angle can have very serious consequences because the device cannot be adjusted in situ, but must be removed and replaced if the selected sleeve strap does not have the correct angle.
None of the above patents show a combination of a femoral plate which provides a pivotal mount for an adjustable angle sleeve, and a pivotable sleeve for insertion into a femoral neck at an optimum angle. The sleeve is then held at that angle by means of a wedge-shaped washer and retaining nut, which are tightly fit onto the outer end of the sleeve.